Earthquakes and Japan (Part I)

The Tokai Earthquake

Plate tectonics

The surface of the earth is covered with dozens of plates, which are like

hard board blocks, fitted together like a jigsaw puzzle.

By the movement of the mantle below the earth’s surface, the plates shift in

certain directions from several to dozen centimeters annually. When these

plates collide, it results in an earthquake and active volcanic activity.

Earthquake Mechanism

By the shifting of the plates, intense amounts of strain are stored incessantly

until it reaches a peak and shatters up the plate, releasing all the pressure in the

form of tremors on the surface of the earth, which we know as an earthquake.

The Tokai Earthquake:

Along the Pacific coast of Japan, huge earthquakes have occurred in a 100-

150 year cycle. In Shizuoka prefecture and the surrounding region, it has been

almost 150 years since the last earthquake occurred in 1854. Therefore, there

is no doubt a big earthquake will hit at any time. In the Tokai region, of which

Shizuoka is the center, a prognostication of the Tokai Earthquake was released

in August 1976, becoming a big social issue. The prefecture, individual

municipalities and each household need to prepare for the earthquake most


Damage Assumption:

To promote effective countermeasures of damage control resulting from an

earthquake, Shizuoka Prefecture has put together a service for estimating

damages that could occur from an earthquake.

Scale Guide: Meteorological Agency Scale Classification Chart (Feb. 1996)

Each scale describes the strength of the earthquake’s tremor, observed by scale

measurement equipment.

Scale Effects on People / Indoor situation / Outdoor situation


People do not feel the tremor. 


A few people indoors feel slight tremor. 


Many people indoors feel the tremor. A few people are awoken from sleep. Hanging objects such as electric lamp shades shake slightly.


Most people indoors feel the tremor. Some may be alarmed. The dishes on shelves may make noise from the shaking. Electric wires shake slightly.

4 People will feel considerable fear and a few try to find shelter in a safe place. Most people will awake from sleep. Hanging objects swing hard. Dishes on shelves make noise. Unstable objects may fall off. Electric wires shake hard. People walking will feel the tremor. People driving cars may feel the tremor.

5 weak

Many people try to find shelter in a safe place. A few feel difficulty in moving. Hanging objects shake hard. Dishes and books may fall off shelves. Unstable objects fall off. Furniture may move. Window glass may break and fall. The shaking of electric poles is visible. Block walls without reinforcementmay break down. Roads may have some damage.

5 strong

People will feel frightened. Many people have difficulty in moving. Many dishes and books may fall off shelves. TV may fall from its stand. Heavy furniture such as closets may collapse. Doors may get jammed and not open. Some doors may come apart from its frame. Many block walls without reinforcement will break down. Automatic vending machines without sufficient support may collapse. Many grave stones collapse. Cars have difficulty driving and many will stop.





6 weak 

It is difficult to stand. Most of the heavy furniture that have not been secured, shifts and collapses. Many doors cannot be opened. Wall tiling and glass windows of many buildings are damaged.

6 strong

People are unable to stand and cannot move except by crawling. Most of the unsecured, heavy furniture shift and collapse. Doors may come apart from its frame and be hurled across the room. Wall tiling and glass windows of many building are damaged. Most of the block walls without reinforcement break down.



People suffer from intense jolts and cannot move by their own will. Most of the furniture shifts greatly and some of them are tossed around. Wall tiling and glass windows of most buildings are damaged. Block walls even with reinforcement may be damaged. 


Source: Guide by the Shizuoka Prefecture Earthquake Disaster Control Center

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